Materials you will need:

Crochet hook: Choose a hook size appropriate for your yarn. The recommended hook size is usually mentioned on the yarn label.
Yarn: Select a yarn suitable for beanies. Worsted weight or chunky yarn is commonly used for this purpose, but you can experiment with different yarn weights for varying results.
Scissors: For cutting yarn.
Tapestry needle: Used for weaving in ends.
Steps to crochet a beanie:

Start with a slip knot: Make a loop with the yarn, insert the hook through the loop, and pull the yarn to tighten the loop around the hook.

Foundation chain: Make a chain of stitches of the desired length. The length depends on the circumference of the head for which you are making the beanie. As a rough guide, a chain of 70-80 stitches for an adult beanie should be sufficient. You can always adjust the size later if needed.

Join the chain: Slip stitch into the first chain stitch to create a circle. Be careful not to twist the chain while joining.

Round 1: Chain one (acts as the first single crochet), then work single crochet stitches all around the circle. Insert the hook into the center of the circle, yarn over, pull the yarn through the loop, yarn over, and pull through both loops on the hook. Repeat this for each stitch around. Slip stitch into the first single crochet to join the round.

Rounds 2 and beyond: Repeat the single crochet stitch in each stitch around the previous round. Continue working in rounds without joining until the desired length of the beanie is achieved. You can add or subtract stitches to adjust the size of the beanie as needed.

Fasten off: When the beanie reaches the desired length, cut the yarn, leaving a long tail. Thread the tail through the tapestry needle, insert the needle under the front loop of each stitch in the last round, and pull tightly to close the top of the beanie.

Finishing touches: Weave in any loose ends using the tapestry needle. You can also add embellishments like pom-poms, buttons, or ribbons to personalize your beanie.